1. Technical Field
The present invention relates to a radiological image detection apparatus.
2. Related Art
An X-ray photographing has been widely distributed in applications such as medical diagnoses, nondestructive inspection and the like. In a general X-ray photographing, an X-ray is irradiated to a subject and attenuated while transmitting at each part of the subject to be detected. An X-ray image of the subject is obtained based on an intensity distribution of the transmitted X-ray.
Recently, as a medium for detecting an X-ray, a flat panel detector (FPD) having a two-dimensional arrangement of pixels for detecting an X-ray and converting the detected X-ray into an electrical signal has been used. In the X-ray photographing, a so-called cassette which is configured to accommodate the FPD in a portable case has been widely used.
In general, various correction processes are performed on image data of a subject acquired by the FPD to present an image based on the corrected image data as the X-ray image of the subject. An example of the correction processes may include an offset correction.
The offset correction removes a dark current noise of each pixel of the FPD, in which the dark current is measured as an electrical signal output from each pixel when there is no input (X-ray exposure) to the FPD. The offset correction removes dark image data generated when there is no input to the FPD, from the X-ray image data generated by detecting the X-ray transmitting the subject, thereby removing different dark current noises from each pixel.
The correction processes using the dark image data may include an afterimage correction or a pixel defect correction, in addition to the offset correction.
The dark current of each pixel is very low and is susceptible to disturbances such as vibration, load, and the like. For example, the stripe-like image spots sometimes may be generated in the dark image generated under vibrations. Meanwhile, when the dark image is removed, the image spots may be generated in the X-ray image. In other words, when the correction process is performed using the dark image data acquired in a situation in which excessive disturbances act, suitable correction may not be performed. Particularly, the cassette is frequently exposed to the disturbances due to a use form thereof. Therefore, for example, an apparatus has been suggested that detects vibration when the vibration is generated and waits until the vibration is stabilized within an allowable range to acquire X-ray image data and dark image data (see, for example, JP-A-2001-340323 and JP-A-2005-245663).
The X-ray photographing apparatus as described in JP-A-2001-340323 and JP-A-2005-245663 acquires the X-ray image data and the dark image data after the detected vibration is stabilized within the allowable range. In other words, it is determined whether the dark image data is acquired together with the acquisition of the X-ray image data. In this case, the allowable range of vibration is typically set in accordance with the dark image data which is significantly affected by the vibration as compared with the X-ray image data.
For example, in performing a continuous photographing while changing photographing portions of the same subject, every time the photographing portions are changed, an X-ray image detection apparatus is vibrated. However, according to the determination whether the image data is acquired as described above, every time the photographing portions are changed, the photographing is not performed until the vibration is stabilized within the allowable range which is set in accordance with the dark image which is significantly affected by the vibration. As a result, the photographing may be delayed.
The present invention has been made in an effort to provide a radiological image detection apparatus capable of performing a suitable correction process for radiological image data and also efficiently progressing a photographing.